A typical data storage system includes a rigid housing having a base and top cover that encloses a variety of components. The components include one or more discs having data surfaces for storage of digital information. The disc(s) are mounted on a spindle motor. The spindle motor causes the disc(s) to spin and the data surfaces of the disc(s) to pass under respective aerodynamic bearing disc head sliders. The sliders carry transducers, which write information to and read information from the data surfaces of the discs.
Recently, there has been a rapid increase in the production of smaller and lighter weight disc drives in the disc drive industry as well as a rapid increase in the areal density of disc(s). These smaller sized disc drives are for use with handheld or portable devices, such as cell phones and digital music players, which are energized by a battery. When producing smaller sized disc drives for portable devices, it is often desirable to include a spindle motor with a high electromagnetic (EM) performance level. Spindle motors having high EM performance levels include low power consumption, a high torque constant (Kt) and a high voltage margin at low temperatures (to overcome start up problems).
In addition, it is desirable to include spindle motors that have small z-heights and fluid dynamic bearings (FDB). Small z-heights allow the disc drive to be as small as possible for use in portable devices. Fluid dynamic bearings in a spindle motor generate much less vibration in comparison to conventional ball bearings. However, spindle motors, having fluid dynamic bearings, consume much more power than that of spindle motors having conventional ball bearings. In general, the power consumption of fluid dynamic bearings can consume 1.5 to 2.0 times more power than conventional ball bearings. Although the use of fluid dynamic bearings in a spindle motor are desirable, the large power consumption of fluid dynamic bearings compromises EM performance levels in the spindle motor.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.